Can Dahlias & Canna Lily Bulbs Be Planted in Shade?

Dahlias, with their bright flowers, love to soak up sun.

Cannas (Canna) and dahlias (Dahlia) are tropical plants, hardy in U.S. Department of Agriculture plant hardiness zones 7 through 10. In cold winter climates, both can be grown as annuals. Alternately, the canna rhizomes and dahlia tubers can be dug up in fall, stored in frost-free locations and replanted in spring. Both plants need warmth and direct sun -- preferably about six hours per day -- to thrive. Planting in shade will not produce good results.

Shade Consequences

Planting dahlias and cannas in shade harms the plants in several ways. The lack of light slows growth, causing dahlias, in particular, to become "leggy," with long, straggly stems. Lack of sunlight also deprives the plants of the warmth they need to produce optimal growth and abundant flowers. Depending on the degree of shade, flowers will be sparse or may not bloom at all. If a plant is showing either poor growth or lack of flowers, it probably needs to be moved to a sunnier location.

Options

Both cannas and dahlias are well suited to container culture. In cold winter climates, growing the plants in containers may even be preferable, as it makes it easier to store them over the winter. Container planting allows them to be grown in any sunny space -- on the edge of an asphalt driveway, in the corner of a deck or patio or in an uncultivated part of a vegetable garden. Large containers can accommodate several dahlia plants or one large canna. Both work in mixed plantings of sun-loving species.

Culture

When selecting sites for cannas and dahlias, make the best of the available sunny options on your property. Any site that will support tomatoes, roses or lavender will also support cannas and dahlias. Protected, south-facing sites are best, because wind can topple stems and harm foliage. Good drainage is another necessity for in-ground plants, as unamended clay soil can cause tubers and rhizomes to rot. If soil is a problem, consider raised beds or containers.

Alternatives

In gardens without sunny space, you can achieve the colorful effects provided by cannas and dahlias by planting other species that are better suited to lower light situations. In partial shade, tuberous begonias (Begonia tuberhybrida), hardy in USDA zones 9 through 11, produce bright-colored flowers in an array of sizes, colors and forms. As with dahlias, the tubers can be dug up in the fall and overwintered. Caladium (Caladium bicolor), hardy in USDA zones 9 through 10, provides colorful foliage in shade, with elephant-ear type leaves in shades of green, pink, red, white and yellow.

About the Author

Elisabeth Ginsburg, a writer with over 20 years' experience, earned an M.A. from Northwestern University and has done advanced study in horticulture at the New York Botanical Garden. Her work has been published in the "New York Times," "Christian Science Monitor," "Horticulture Magazine" and other national and regional publications.